How Watts Bar Works
All power plants convert a source of energy or fuel into electricity. Most large plants do that by heating water to create steam, which turns a turbine that drives an electric generator. Inside the generator, a large electromagnet spins within a coil of wire, producing electricity.
A fossil plant burns coal or oil to make the heat that creates the steam. Nuclear power plants, like Watts Bar make the steam from heat that is created when atoms split apart – called fission.
The fuel for nuclear power plants is uranium, which is made into pellets and sealed inside long metal tubes, called fuel rods. The rods are located in the reactor vessel.
The fission process takes place when the nucleus of a uranium atom is split when struck by a neutron. The“fissioning” of the nucleus releases two or three new neutrons and energy in the form of heat. The released neutrons then repeat the process, releasing more neutrons and producing more nuclear energy. The repeating of the process is called a chain reaction and creates the heat needed to turn water into steam.
In a pressurized water reactor, like Watts Bar Unit 1, water (yellow) is pumped through the reactor core and heated by the fission process. The water is kept under high pressure inside the reactor so it does not boil.
The heated water from the reactor passes through tubes inside four steam generators, where the heat is transferred to water flowing around the tubes. The water (pink) boils and turns to steam.
The steam is piped to the turbines. The force of the expanding steam drives the turbines, which spin a magnet in coil of wire – the generator– to produce electricity.
After passing through the turbines, the steam is converted back to water by circulating it around tubes carrying cooling water in the condenser. The condensed steam – now water – is returned to the steam generators to repeat the cycle.
The cooling water from the condenser is sprayed into the air inside the cooling tower and falls about 60 feet, which cools it before it is continuously recycled to condense more steam. Water in the vapor rising from the cooling tower is replenished to the condenser cooling system using water from the Tennessee River.
The three water systems at Watts Bar are separate from each other, and the radioactive water (yellow) is not permitted to mix with other nonradioactive water systems.